Orlando , Florida -LRB- CNN -RRB- -- A whale trainer at SeaWorld died from `` multiple traumatic injuries and drowning '' after a 12,000-pound killer whale grabbed her ponytail and pulled her underwater in front of shocked onlookers at Shamu Stadium , the Orange County Sheriff 's office said Thursday .

Dawn Brancheau , 40 , was `` pulled underwater for an extended period of time , '' by the whale , Chuck Tompkins , SeaWorld 's curator of zoological operations , told CNN 's `` American Morning . ''

The county medical examiner ruled Brancheau `` most likely died from multiple traumatic injuries and drowning after one of the park 's killer whales pulled her into a pool behind Shamu Stadium , '' the sheriff 's office said in a statement .

The statement confirms Tompkins ' account , saying that Brancheau was interacting with the whale , named Tilikum , in knee-deep water `` when the animal grabbed her by the hair , said to be in a long ponytail , and pulled her underwater . ''

Rescuers were not immediately able to reach Brancheau because of the `` whale 's aggressive nature , '' the sheriff 's office said . She was recovered by SeaWorld staff members after Tilikum was coaxed into a smaller pool and lifted out of the water by a large platform on the bottom of the smaller tank , authorities said .

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`` While this incident remains the subject of an ongoing death investigation , there are no signs of foul play , '' the sheriff 's statement said . `` All evidence and witness statements indicate that the death was a tragic accident . ''

Earlier accounts varied on how Brancheau ended up in the tank .

A witness told CNN affiliate WKMG-TV that the whale approached the glass side of the 35-foot-deep tank at Shamu Stadium , jumped up and grabbed Brancheau by her waist , shaking her so violently that her shoe came off . A SeaWorld employee , who asked not to be identified , described the incident the same way .

Orange County Sheriff 's Office spokesman Jim Solomons said Brancheau slipped into the tank .

Tilikum has been linked to two other deaths . He and two other whales were involved in the drowning of a trainer at a Victoria , British Columbia , marine park in 1991 . The trainer fell into the whale tank at the Sea Land Marine Park Victoria and was dragged underwater as park visitors watched .

In 1999 , Tilikum was blamed for the death of a 27-year-old man whose body was found floating in a tank at SeaWorld , the apparent victim of a whale 's `` horseplay , '' authorities said then .

The Orange County Sheriff 's Office said the man apparently hid in the park until after it closed , then climbed into the tank .

The 22-foot-long whale was `` not accustomed to people being in his tank '' and `` would n't have realized he was dealing with a very fragile human being , '' Solomons said at the time .

iReport : Photo taken moments before Sea World incident

Because of Tilikum 's history , as well as his size , trainers did not get into the water with him , Tompkins told CNN . Specific procedures were in place for working with him , he said , although `` obviously , we need to evaluate those protocols . ''

`` He 's just a really , really large animal , '' Tompkins said , noting that female killer whales weigh 6,000 pounds -- half of Tilikum 's weight . `` Just because of his size alone , it would be dangerous to get in the water with him . '' But the whale 's previous incidents were also taken into account , he said .

Tompkins pointed out that the 1991 incident occurred before SeaWorld owned Tilikum and that no one is sure what took place in the incident eight years later .

Tilikum could have been trying to play with Brancheau or get her attention or companionship , said Nancy Black , a marine biologist who has studied whales for 20 years . Such whales play with seals and sea lions in the wild , tossing them in the air , she said . But they do not kill them and end up letting them go .

`` I do n't believe the killer whale purposely intended to kill the woman , '' she said . `` It was more likely an accident , I would guess . '' But , she said , the whale could also have been frustrated for some reason .

Tompkins said there were no indications of any problem with Tilikum or any other animal just before the incident , and that Brancheau `` had done a great session with him ... he seemed to enjoy what he was doing at the time . ''

The incident , however , raises larger questions regarding the captivity of wild animals .

A spokesman for People for the Ethical Treatment of Animals called the death `` a tragedy that did n't have to happen . ''

Jaime Zalac said the organization had called on SeaWorld `` to stop confining oceangoing mammals to an area that to them is like the size of a bathtub , and we have also been asking the park to stop forcing the animals to perform silly tricks over and over again . It 's not surprising when these huge , smart animals lash out . ''

Black told CNN that killer whales in the wild live in family groups , and males stay with their mothers their entire lives . Family members rely on each other for social structure and play , and they cover hundreds of miles of ocean , she said .

`` I think they do need more space , and situations like that do cause a lot of stress for them , most likely . '' She said Tilikum had a `` flopped fin , '' something seen in captivity but not much in the wild .

But Tompkins said , `` We have a tremendous track record with these animals at SeaWorld '' and a very small percentage of problems . It 's useful to have animals in the park , he said , because it gives scientists a chance to study them and gives members of the public an opportunity to see them and learn about them .

`` This is the first time in 46 years that we 've ever had an incident like this with a trainer , '' he said . Although Tilikum is large and has to be handled carefully , `` to mark him as a killer is unfair . ''

In 2006 , a trainer at the adventure park was hospitalized after a killer whale grabbed him and twice held him underwater during a show at Shamu Stadium .

CNN 's John Couwels and Brian Todd contributed to this report .

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Whale shows canceled Thursday at SeaWorld

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Trainer Dawn Brancheau , 40 , fatally injured by killer whale at SeaWorld Orlando

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The whale , Tilikum grabbed her ponytail , pulled her underwater

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Tilikum has been linked to two other deaths